Electrodes located at storage capacitor wiring in active matrix substrate

ABSTRACT

An active matrix substrate includes a thin film transistor, a scanning signal line, and a data signal line disposed on the substrate. A gate electrode of the transistor is connected to the scanning signal line, a source electrode thereof is connected to the data signal line, and a drain electrode thereof is connected to a pixel electrode; and an upper electrode is disposed so as to oppose a storage capacitor wiring pattern at least via an insulating layer. Within a pixel region, the upper electrode includes three divided electrodes in a region opposing the storage capacitor wiring pattern, and a central divided electrode of the three divided electrodes has the smallest area.

REFERENCE TO RELATED APPLICATIONS

This is a divisional of application Ser. No. 11/041,361, filed Jan. 25,2005, now U.S. Pat. No. 7,430,024 which claims priority under 35 U.S.C.§119(a) on Patent Application No. 2004-20488 filed in Japan on Jan. 28,2004 and No. 2004-349590 filed in Japan on Dec. 2, 2004, the entirecontents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an active matrix substrate and adisplay device. More particularly, it relates to an active matrixsubstrate provided with a thin film transistor and a storage capacitorelement at each pixel for driving the liquid crystal layer, and to anactive matrix type liquid crystal display device.

2. Description of the Related Art

Active matrix substrates are widely used in active matrix type displaydevices such as liquid crystal display devices and electroluminescence(EL) display devices. In the conventional active matrix type liquidcrystal display devices using such active matrix substrates, a pluralityof scanning signal lines and a plurality of data signal linesintersecting with the scanning signal lines are disposed on eachsubstrate, and a thin film transistor (hereinafter also referred to as“TFT”), among others, is disposed at each point of intersection. Animage signal is transmitted to each pixel unit by the switching functionof the TFT and so forth. It has also been disclosed that each pixel unitbe provided with a storage capacitor element (cf. e.g. Japanese KokaiPublication H06-95157, page 1). Such storage capacitor element preventsthe image signal from deteriorating due to the self discharge of theliquid crystal layer or the OFF-state current in the TFT during the OFFperiod of the TFT. Further, the storage capacitor element is utilizednot only for storing an image signal during the OFF period of the TFTbut also as a route for applying any of various modulated signals inliquid crystal driving, for instance. A liquid crystal display deviceequipped with storage capacitor elements can realize low electricityconsumption and high picture quality.

An example of the structure of a conventional active matrix substrate isnow described referring to the drawings.

FIG. 4 is a schematic plan view illustrating the constitution of onepixel in an active matrix substrate equipped with a storage capacitorelement and used in a conventional active matrix type liquid crystaldisplay device.

In FIG. 4, a plurality of pixel electrodes 51 are disposed to form amatrix in an active matrix substrate, and a scanning signal line 52 forfeeding a scanning signal and a data signal line 53 for feeding a datasignal are disposed surrounding those pixel electrodes 51 andintersecting with each other. At each point of intersection of thescanning signal line 52 and data signal line 53, there is disposed a TFT54 as a switching element to be connected to the pixel electrode 51. Thescanning signal line 52 is connected to the gate electrode of that TFT54, and the TFT 54 is driven and controlled by the scanning signalinputted into the gate electrode. Further, the data signal line 53 isconnected to the source electrode of the TFT 54, and a data signal isinputted into the source electrode of the TFT 54. Furthermore, to thedrain electrode, there are connected an interconnection electrode 55,one electrode (storage capacitor upper electrode) 55 a of a storagecapacitor element via the interconnection electrode 55, and the pixelelectrode 51 via a contact hole 56. A storage capacitor (common) wiringpattern 57 functions as the other electrode (storage capacitor lowerelectrode) of that storage capacitor element.

FIG. 5 is a schematic sectional view illustrating a section of theactive matrix substrate shown in FIG. 4 as cut along the line A-A′.

In FIG. 5, there is seen a gate electrode 62 disposed on a transparentinsulating substrate (insulator substrate) 61 made of glass, plastic orlike material and connected to a scanning signal line 52. The scanningsignal line 52 and gate electrode 62 are formed of a film or layer of ametal such as titanium, chromium, aluminum or molybdenum or an alloythereof, or a laminate thereof. The storage capacitor (common) wiringpattern 57, which constitutes the other electrode of the storagecapacitor element (storage capacitor lower electrode), is made of thesame material as the scanning signal line 52 and gate electrode 62. Agate insulator (gate insulating layer) 63 is disposed to cover the same.The gate insulator 63 is made of an insulation layer such as a siliconnitride or silicon oxide layer. Thereon are disposed, in a manneroverlapping with the gate electrode 62, a high-resistivity semiconductorlayer 64 made of amorphous silicon, polysilicon or the like, and alow-resistivity semiconductor layer consisting of n⁺amorphous silicon orthe like doped with such an impurity as phosphorus and coming to asource electrode 66 a and a drain electrode 66 b. Further, a data signalline 53 is disposed so as to connect to the source electrode 66 a.Furthermore, an interconnection electrode 55 is disposed so as toconnect to the drain electrode 66 b, and the interconnection electrode55 is extended to constitute a storage capacitor upper electrode 55 a,which is one of the electrodes of the storage capacitor element, and isconnected to a pixel electrode 51 via a contact hole 56. The data signalline 53, interconnection electrode 55 and storage capacitor upperelectrode 55 a are made of the same material, and a layer of a metalsuch as titanium, chromium, aluminum or molybdenum or an alloy thereof,or a laminate thereof is used as the material. The pixel electrode 51 isformed, for example, of a transparent conductive layer such as an ITO(indium tin oxide), IZO (indium zinc oxide), zinc oxide or tin oxidelayer. The contact hole 56 is formed so as to pass through an interlayerinsulating film or layer 68 formed to cover the top of each of the TFT54, scanning signal line 52, data signal line 53 and interconnectionelectrode 55. The material of the interlayer insulating layer 68 is, forexample, an acrylic resin, silicon nitride, or silicon oxide. An activematrix substrate having such a structure as shown in FIGS. 4 and 5 isdisclosed, for example, in Japanese Kokai Publication H09-152625, pages8-11 and 19, drawings 3 and 4.

In an active matrix substrate having such a structure, the storagecapacitor (common) wiring pattern (storage capacitor lower electrode)and scanning signal line are formed in one and the same step, and thestorage capacitor upper electrode, data signal line and interconnectionelectrode are formed in one and the same step for the purposes ofsimplifying the manufacturing step and reducing the production cost.Further, when the pixel electrode is formed on an interlayer insulatinglayer, as shown in FIG. 5, the pixel electrode can be overlapped witheach signal line, so that the aperture ratio can be increased and,further, the effect of shielding the pixel electrode against theelectric field of each signal line can also be produced. On thatoccasion, the connection between the pixel electrode and drain electrodeis secured via the interconnection electrode by forming a contact holein the interlayer insulating layer on the storage capacitor (common)wiring pattern or scanning signal line pattern to thereby connect thepixel electrode to the storage capacitor upper electrode. The positionof the contact hole is not restricted to a site on the storage capacitorupper electrode but may be on the interconnection electrode. However, asshown in FIG. 4, the contact hole is preferably formed at the site ofthe storage capacitor upper electrode on a pattern of the storagecapacitor (common) wiring pattern, since the aperture ratio is notfurther reduced thereby.

In the storage capacitor element in the active matrix substrate as shownin FIGS. 4 and 5, the presence of a conductive foreign material or apinhole in the insulating layer between the storage capacitor wiringpattern (storage capacitor lower electrode) and storage capacitor upperelectrode may result in a short circuit between the storage capacitorwiring pattern (storage capacitor lower electrode) and the storagecapacitor upper electrode, which, in turn, result in a dot defect at thesite of the short-circuited pixel in the image displayed; in thisrespect, there is room for improvement. Further, in the case ofshort-circuiting between the data signal line and storage capacitorupper electrode, which are formed in one and the same step, due to sucha defect as a residual layer, a dot defect may appear in the same mannerand the defect cannot be repaired; in this respect, there is also roomfor improvement.

As the countermeasure for such a dot defect, the method comprisingdividing the storage capacitor wiring pattern in the pixel and themethod comprising disposing a redundant line in the storage capacitorwiring pattern are disclosed (cf. e.g. Japanese Kokai PublicationH01-303415, pages 2-4, drawing 1 and Japanese Kokai PublicationH09-222615, pages 3, 4, 6 and 7, drawings 1-3).

In the active matrix substrate in which the storage capacitor wiringpattern is made redundant according to the method of dividing thestorage capacitor wiring pattern in the pixel as disclosed in JapaneseKokai Publication H01-303415, the storage capacitor (common) wiringpattern is partly multiplied within each pixel and, further, there isprovided a structure such that when a conductive foreign material or apinhole occurs in the insulating layer between the storage capacitorwiring pattern (storage capacitor lower electrode) and storage capacitorupper electrode and causes short-circuiting, the short-circuited storagecapacitor wiring pattern (storage capacitor lower electrode) can bedestructed and eliminated by means of a laser, for instance.

However, these methods can indeed destruct and eliminate ashort-circuited storage capacitor wiring pattern (storage capacitorlower electrode) by means of a laser, for instance, upon occurrence of ashort circuit between the storage capacitor wiring pattern and storagecapacitor upper electrode due to the presence of a conductive foreignmaterial or a pinhole in the insulating layer between the storagecapacitor wiring pattern (storage capacitor lower electrode) and storagecapacitor upper electrode but it is difficult to attain such destructionand elimination without damaging the insulating layer; in this respect,there is room for improvement. Further, when the storage capacitor upperelectrode formed in the same step together with the data signal line isshort-circuited with the data signal line due to a residual layer, forinstance, the short-circuited storage capacitor upper electrode cannotbe repaired while allowing the same as a storage capacitor elementwithout resulting in a dot defect; in this respect, there is room forimprovement.

Further, a method comprising constituting the storage capacitorelectrode as an at least three-layer structure through the intermediaryof insulating layers has been disclosed (cf. e.g. Japanese KokaiPublication H07-270824, pages 6-8, drawings 10 and 11). According tothis method, the middle layer electrode (storage capacitor lowerelectrode) of the storage capacitor electrode formed in the form of atleast three layers is divided into a plurality of sections and eachsection is connected to the lower layer electrode (storage capacitorlower electrode) via a contact hole. This gives a structure such that amiddle layer electrode (storage capacitor lower electrode)short-circuited with the upper layer electrode (storage capacitor upperelectrode) can be destructed and eliminated from the lower layerelectrode (storage capacitor lower electrode) by means of a laser or thelike and, in the case of a short circuit formed between the storagecapacitor element electrodes, the short-circuited storage capacitorelectrodes are partly destructed and eliminated by means of a laser orthe like; the short circuit of the storage capacitor electrodes can bethus repaired to an extent such that the short circuit of the storagecapacitor electrodes will not affect the display quality.

However, this method gives a structure such that each middle layer of aplurality of the divided storage capacitor lower electrodes is connectedto the lower storage capacitor electrode in the lower layer via acontact hole and the storage capacitor upper electrode in the upperlayer is used as a pixel electrode and, therefore, a simplification ofthe manufacturing process and a reduction of the manufacturing cost havebeen demanded.

Furthermore, a liquid display device having a first region comprising anauxiliary capacitor electrode (storage capacitor upper electrode)electrically connected to an interconnection wiring pattern(interconnection electrode) and to a contact hole, a third region formedat a site not overlapping with the auxiliary capacitor common wiringpattern (storage capacitor wiring pattern), and a second regionelectrically connected to the first region via that third region (cf.e.g. Japanese Kokai Publication 2001-330850, page 1). According to thisconstruction, it is possible, when one of the first and second regionsis short-circuited, to function the other region as a storage capacitorelement by destructing and eliminating the short-circuited region.

However, the storage capacitor upper electrode formed in the same stepas the data signal line is readily short-circuited with the data signalline due to a residual layer or the like, and the method described inJapanese Kokai Publication 2001-330850 cannot repair the first andsecond regions simultaneously in case of short-circuiting of both ofthem; in this respect, there is room for contrivance. Furthermore, whenthe first region of the auxiliary capacitor electrode, which is a partof the storage capacitor element, is short-circuited with the datasignal line due to a residual layer, for instance, or when the firstregion is short-circuited, between layers, with the auxiliary capacitorcommon wiring pattern (storage capacitor wiring pattern) due to apinhole or a conductive foreign material, the method described inJapanese Kokai Publication 2001-330850 requires that cleavage be made atthe cleavage site X1 in the third region (cf. FIG. 1 in Japanese KokaiPublication 2001-330850) and at the cleavage site X3 of theinterconnection wiring pattern (cf. FIG. 1 in Japanese Kokai Publication2001-330850) and the connection points Y1 and Y2 (cf. FIG. 1 in JapaneseKokai Publication 2001-330850) be electrically connected to connect theinterconnection wiring pattern to the second region via aninterconnection electrode for repairing; thus, it is necessary to carryout laser irradiation at a total of 4 sites. Therefore, there is stillroom for contrivance for shortening the time of repairing and the stepof repairing.

SUMMARY OF THE INVENTION

It is an object of the present invention, which has been made in view ofthe above-discussed problems, to provide an active matrix substrate inwhich faulty connections in storage capacitor elements as caused by ashort circuit between storage capacitor electrodes due to a conductiveforeign material or a pinhole in the insulating layer or by a shortcircuit between a data signal line and a storage capacitor upperelectrode can be repaired with ease and a display device in which suchactive matrix substrate is used.

The present inventors made various investigations in search of an activematrix substrate in which faulty connections in storage capacitorelements can be repaired with ease and paid their attention to the factthat faulty connections are caused by short-circuiting of both ends of astorage capacitor upper electrode with a data signal line formed in thesame step. And, they came to realize that when the storage capacitorupper electrode is divided into at least three, the function of thestorage capacitor element can be maintained, even in the case ofshort-circuiting of the divided electrode occurring at both ends withthe data signal line, by electrically separating the short-circuiteddivided electrode for effective functioning of the remaining dividedelectrode, and they have now completed the present invention.

Thus, the present invention provides an active matrix substratecomprising a thin film transistor disposed at the crossing point of ascanning signal line with a data signal line on the substrate, with agate electrode of the transistor being connected to the scanning signalline, a source electrode thereof being connected to a data signal lineand a drain electrode thereof being connected to a pixel electrode, anda storage capacitor upper electrode disposed so as to oppose a storagecapacitor wiring pattern at least via an insulating layer, wherein thestorage capacitor upper electrode comprises at least three dividedelectrodes in the region opposing the storage capacitor wiring patternand each divided electrode is connected to the pixel electrode.

The invention also provides an active matrix substrate comprising a thinfilm transistor disposed at the crossing point of a scanning signal linewith a data signal line on the substrate, with a gate electrode of thetransistor being connected to the scanning signal line, a sourceelectrode thereof being connected to the data signal line and a drainelectrode thereof being connected to an interconnection electrode, and astorage capacitor upper electrode disposed so as to oppose a storagecapacitor wiring pattern at least via an insulating layer and connectedto an interconnection electrode and a pixel electrode, wherein thestorage capacitor upper electrode comprises at least three dividedelectrodes in the region opposing the storage capacitor wiring pattern.

The invention further provides an active matrix substrate comprising athin film transistor disposed at the crossing point of a scanning signalline and a data signal line on the substrate, with a gate electrode ofthe transistor being connected to the scanning signal line, a sourceelectrode thereof being connected to the data signal line and a drainelectrode thereof being connected to a pixel electrode, and a storagecapacitor upper electrode disposed so as to oppose the scanning signalline at least via an insulating layer, wherein the storage capacitorupper electrode comprises at least three divided electrodes in theregion opposing the scanning signal line and each divided electrode isconnected to the pixel electrode.

The invention further provides an active matrix substrate comprising athin film transistor disposed at crossing point of a scanning signalline with a data signal line on the substrate, with a gate electrode ofthe transistor being connected to the scanning signal line, a sourceelectrode thereof being connected to the data signal line and a drainelectrode thereof being connected to an interconnection electrode, and astorage capacitor upper electrode disposed so as to oppose the scanningsignal line at least via a insulating layer and connected to theinterconnection electrode and a pixel electrode, wherein the storagecapacitor upper electrode comprises at least three divided electrodes inthe region opposing the scanning signal line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view showing the constitution of one pixel inan active matrix substrate in a preferred mode of embodiment of theinvention (Cs-on-Common system).

FIG. 2 is a schematic sectional view showing a section of the activematrix substrate shown in FIG. 1 as cut along the line D-D′ in FIG. 1.

FIG. 3 is a schematic plan view showing the constitution of one pixel inan active matrix substrate in a preferred mode of embodiment of theinvention (Cs-on-Gate system).

FIG. 4 is a schematic plan view showing the constitution of one pixel ona conventional active matrix substrate.

FIG. 5 is a schematic sectional view showing a section of the activematrix substrate shown in FIG. 4 as cut along the line A-A′ in FIG. 4.

FIG. 6 is a schematic plan view showing the constitution of one pixel onthe active matrix substrate described in Example 3.

FIG. 7 is a schematic plan view showing the constitution of one pixel onthe active matrix substrate described in Example 4.

DETAILED DESCRIPTION OF THE INVENTION

The active matrix substrate of the invention comprises a thin filmtransistor and a storage capacitor upper electrode. Such a thin filmtransistor is disposed at crossing point of a scanning signal line witha data signal line on the substrate, with a gate electrode thereof isconnected to the scanning signal line, a source electrode thereof isconnected to the data signal line and a drain electrode thereof isconnected to a pixel electrode or interconnection electrode. The thinfilm transistors can be used as switches for sampling data signalssimultaneously fed to a plurality of data signal lines by the scanningsignals successively fed to a plurality of scanning lines crossing withthe data signal lines.

In cases where the drain electrode of a thin film transistor is(directly) connected to a pixel electrode and the drain electrode andpixel electrode are disposed in different layers via an insulatinglayer, the drain electrode is connected to the pixel electrode via acontact hole (conductive route for interlayer conduction). In caseswhere the drain electrode is connected to an interconnection electrode,the interconnection electrode and the pixel electrode are connected to astorage capacitor upper electrode. In that case, it is desirable thatthe interconnection electrode and storage capacitor upper electrode beconnected to each other and at least one of the interconnectionelectrode and storage capacitor upper electrode be connected to thepixel electrode via a contact hole. Namely, the pixel electrode may bedirectly connected to the interconnection electrode or directlyconnected to the storage capacitor upper electrode provided that it iselectrically connected to the thin film transistor and storage capacitorupper electrode.

The storage capacitor upper electrode is disposed in a manner opposingthe storage capacitor wiring pattern at least via an insulating layerand constitutes a storage capacitor element with them. As a preferredmode of such a storage capacitor wiring on a Cs-on-Common system, theremay be mentioned the mode comprising a plurality of storage capacitor(common) wiring patterns disposed in parallel to the scanning signallines. Each storage capacitor element can store a data signal fed toeach data signal line, since the storage capacitor upper electrode isconnected to the relevant thin film transistor via an interconnectionelectrode or pixel electrode. The storage capacitor upper electrodes aregenerally formed by forming a metal layer or like conductive layer bysputtering, followed by photolithography and etching.

The constitution of the active matrix substrate of the invention is notparticularly restricted provided that it comprises such constituentelements as mentioned above as essential constituents. Thus, it maycomprise or not comprise another or other constituent elements.

In accordance with the invention, a storage capacitor upper electrodecomprises at least three divided electrodes in the region opposing thestorage capacitor wiring pattern. Thus, the storage capacitor upperelectrode is divided into at least three sections in the region occupiedby the pattern of the storage capacitor wiring pattern. Each of thedivided storage capacitor upper electrode (divided electrode)constitutes a storage capacitor element as a part of the storagecapacitor upper electrode. Therefore, in the mode of the drain electrodeof a thin film transistor being (directly) connected to a pixelelectrode, the above divided electrodes are respectively connected tothe pixel electrode. In the mode of the drain electrode being connectedto an interconnection electrode, the interconnection electrode isconnected to at least one of the divided electrodes and all the dividedelectrodes are connected to a pixel electrode directly via a contacthole or to the pixel electrode via an interconnection electrode.

Such a constitution makes it possible to electrically separate onlydivided electrode containing a short-circuited site and allow theremaining divided electrode(s) to effectively function to therebymaintain the function of the storage capacitor element even in the caseof short-circuiting of the storage capacitor upper electrode with thestorage capacitor wiring pattern or with the data signal line formed inone and the same step as a result of occurrence of a conductive foreignmaterial or a pinhole in the insulating layer between the storagecapacitor wiring pattern and storage capacitor upper electrode.Generally, both end portions of a storage capacitor upper electrode aresusceptible to short-circuiting because of there being disposed a datasignal line, among others. Even when the divided electrodes at both endsare both short-circuited, however, it is now possible to allow theremaining divided electrode(s) to function effectively and therebymaintain the function of the storage capacitor element, since thestorage capacitor upper electrode is divided into at least threesections in accordance with the present invention. By using such anactive matrix substrate as the pixel electrode substrate of a liquidcrystal display device or the like, it become possible to effectivelyprevent dot defects in images displayed from occurring due to storagecapacitor upper electrode short-circuiting, prevent the display qualityof the display device from deteriorating, and improve the yield. Thus,it can be adequately used in providing a liquid crystal panel for alarge-size liquid crystal television or the like which is required tohave a high level of panel quality.

The shape or shapes and the manner of disposition of the above dividedelectrodes are not particularly restricted but there may be mentioned,among others, the mode in which three or more square or rectangulardivided electrodes are juxtaposed with one another and the mode in whichtwo or more square or rectangular divided electrodes are juxtaposed witheach other or one another in one frame-shaped divided electrode.

In the practice of the invention, the storage capacitor upper electrodemay be disposed so as to oppose a scanning signal line at least via ainsulating layer (gate insulator) and comprise at least three dividedelectrodes in the region opposing the scanning signal line. In suchCs-on-Gate system in which the scanning signal line is used as thestorage capacitor lower electrode in the storage capacitor element, too,the effects of the invention can be produced in the same manner as inthe Cs-on-Common system in which a storage capacitor wiring pattern isdisposed as the storage capacitor lower electrode.

Preferred embodiments of the active matrix substrate of the inventionare described below.

When interconnection electrodes are disposed in the practice of theinvention, the active matrix substrate is preferably one such thatinterconnection electrode is connected to each of the divided electrodesand, in case of short-circuiting of one of the divided electrodes, theinterconnection electrode connected to the short-circuited dividedelectrode become separated and that divided electrode becomeelectrically separated from the other divided electrodes. In accordancewith the invention, any short-circuited divided electrode can beelectrically separated with ease according to need, for example in thecase of short-circuiting of the divided electrode, by partly destructingand separating the interconnection electrode in question by means of alaser or the like. In the practice of the invention, when there is nointerconnection electrode disposed, the above-mentioned active matrixsubstrate is preferably one such that the divided electrodes arerespectively connected to a pixel electrode via a contact hole and, inthe case of short-circuiting of one divided electrode, the dividedelectrode is separated form the pixel electrode and the dividedelectrode is thereby electrically separated from the other dividedelectrodes. When such an active matrix substrate is used as the pixelelectrode substrate of a display device, dot defects due toshort-circuiting are repaired in a state close to normal pixels.

In the practice of the invention, each interconnection electrodepreferably has at least two routes. As typical modes of such aninterconnection electrode, there may be mentioned (1) the mode in whichone interconnection electrode connected to a thin film transistorramifies into two or more branches to be connected to a storagecapacitor upper electrode, (2) the mode in which two or moreinterconnection electrodes connected to a thin film transistor arecombined into one to be connected to a storage capacitor upperelectrode, and (3) the mode in which two or more interconnectionelectrodes connected to a thin film transistor are connected, with orwithout cross linking, to a storage capacitor upper electrode. Amongthem, the mode (3) is preferred. When the interconnection electrode isgiven such a form, the data signal from a thin film transistor is sentto the relevant storage capacitor upper electrode via two or more routesand, therefore, the possibility of the thin film transistor and storagecapacitor upper electrode being insulated from each other due to partialdisconnection of the interconnection electrode can be reduced. When suchan active matrix substrate is used as the pixel electrode substrate of adisplay device such as a liquid crystal display device, the occurrenceof dot defects in displayed images as resulting from disconnection ofinterconnection electrodes can be effectively prevented, the displayquality of the display device can be prevented from deteriorating, andthe yield can be improved.

In cases where interconnection electrodes are disposed in the practiceof the invention, each storage capacitor upper electrode is preferablyconnected to a pixel electrode via at least one contact hole disposed onat least one of the divided electrodes. When an active matrix substrateis used in a liquid crystal display device or the like, either of thesites of contact hole formation or the sites of storage capacitor upperelectrode formation are difficult to utilize as aperture sites. Bydisposing these on the same sites on the substrate, it becomes possibleto increase the aperture ratio. The contact hole is not particularlyrestricted provided that it can electrically connect the dividedelectrodes to the relevant pixel electrode. When the divided electrodesand pixel electrode are disposed via an insulating layer, it may be aconductive material, such as a metal, formed on the inside wall of athrough hole penetrating the insulating layer or a conductive materialfilled within the through hole, for instance.

When interconnection electrodes are disposed in the practice of theinvention, the divided electrode or electrodes to be equipped with theabove-mentioned contact hole may be adequately selected according to thedistance between the data signal line and divided electrode(s), and theshape and manner of disposition of the divided electrode(s). Aspreferred modes of the contact hole, there may be mentioned, amongothers, (1) the mode in which it is disposed on at least one of thedivided electrodes occurring (located) at both ends, (2) the mode inwhich it is disposed on at least one of the divided electrodes otherthan the divided electrodes occurring at both ends, and (3) the mode inwhich it is disposed at least on each of the divided electrodesoccurring at both ends. In many cases, the divided electrodes occurringat both ends are close to the relevant data signal line, hence aresusceptible to short-circuiting with the data signal line. When adivided electrode on which no contact hole is disposed isshort-circuited with the data signal line, however, it is not necessaryto eliminate the pixel electrode on the contact hole but it is possibleto electrically separate the short-circuited divided electrode from theother divided electrodes with ease by destructing and separating a partof the interconnection electrode by means of a laser, for instance and,thus, the short circuit between the data signal line and the drainelectrode of the thin film transistor can be repaired. On the contrary,when a divided electrode on which a contact hole is disposed isshort-circuited with the data signal line, repairs may become difficultto carry out in some instances; it becomes necessary to repair the shortcircuit between the data signal line and the pixel electrode on thecontact hole, for example, by eliminating the pixel electrode on thecontact hole.

In the above-mentioned mode (1), one (the other) of the dividedelectrodes occurring at both ends is not equipped with a contact holeand, accordingly, the possibility of short-circuiting of the dividedelectrode, on which a contact hole is formed, with the data signal linecan be reduced. In the above-mentioned mode (2), either of both thedivided electrodes occurring at both ends is not equipped with a contacthole and, accordingly, the possibility of short-circuiting of thedivided electrode, on which a contact hole is formed, with the datasignal line can be more effectively reduced. On the contrary, in theabove-mentioned mode (3), the number of contact holes can be increasedand the reliability of connection between the storage capacitor upperelectrode and pixel electrode can be increased. when the distancebetween the data signal line and divided electrodes occurring at bothends is great, for instance, the mode (3) is preferred.

As for the storage capacitor upper electrode mentioned above, thedivided electrodes occurring at both ends of the storage capacitor upperelectrode are preferably smaller in the total area of the regionopposing the storage capacitor wiring pattern or scanning signal line ascompared with the other divided electrode or electrodes. In this case,when there are two or more other divided electrodes, the sum of theareas overlapping between their electrodes and the storage capacitorwiring pattern or scanning signal line is used in comparing with the sumof the areas overlapping between the divided electrodes occurring atboth ends and the storage capacitor wiring pattern or scanning signalline. In this mode, the divided electrodes occurring at both ends whereshort-circuiting with the data signal line tends to occur are madesmall, so that even if these divided electrodes are electricallyseparated as a result of short circuit repair, the decrease in thecapacity of the storage capacitor element can be reduced. Further, whenthe divided electrodes not occurring at either end are the same in size,it is also possible to increase the distance between the dividedelectrodes occurring at both ends and the data signal line to therebyprevent the short-circuiting of the divided electrodes occurring at bothends.

Further, when interconnection electrodes are provided in the practice ofthe invention, the storage capacitor upper electrode is preferably suchthat the divided electrode provided with a contact hole is small inarea. This makes it possible to reduce the possibility ofshort-circuiting between the divided electrode provided with a contacthole and the storage capacitor wiring pattern or scanning signal line.More preferably, the storage capacitor upper electrode consists of atleast three divided electrodes in the region opposing the storagecapacitor wiring pattern or scanning signal line and is connected to apixel electrode via at least one contact hole disposed on the dividedelectrode not occurring at either end and the divided electrode providedwith the contact hole is smaller in the area of the region opposing thestorage capacitor wiring pattern or scanning signal line as comparedwith the divided electrode(s) occurring at both ends. In this case, thecomparison is made between the divided electrode smallest in the area ofthe region opposing the storage capacitor wiring pattern or scanningsignal line out of the divided electrodes occurring at both ends and thedivided electrode greatest in the area of the region opposing thestorage capacitor wiring pattern or scanning signal line out of thedivided electrodes equipped with a contact hole (if there are two ormore such divided electrodes). In this mode, the area of the dividedelectrode provided with a contact hole is made small and neither of thedivided electrodes occurring at both ends is provided with a contacthole, so that the possibility of short-circuiting of the dividedelectrode, on which a contact hole is formed, with the storage capacitorwiring pattern or scanning signal line and with the data signal line isreduced. Still more preferably, the storage capacitor upper electrodehas a form such that it comprises three or more divided electrodes inthe region opposing the storage capacitor wiring pattern or scanningsignal line and is connected to a pixel electrode via one or morecontact holes disposed on the divided electrode or electrodes notoccurring at either end and the divided electrode or electrodes otherthan the divided electrodes occurring at both ends are smaller in thearea of the region opposing the storage capacitor wiring pattern orscanning signal line than the divided electrodes occurring at both ends.In this case, the area comparison is made between the divided electrodesmaller in the area of the region opposing the storage capacitor wiringpattern or scanning signal line out of the divided electrodes occurringat both ends and the divided electrode greatest in the area of theregion opposing the storage capacitor wiring pattern or scanning signalline out of the divided electrodes not occurring at either end (if thereare two or more such divided electrodes).

The present invention further relates to a display device equipped withthe above-mentioned active matrix substrate. In such display device, theabove active matrix substrate is used as a pixel electrode substrateand, therefore, the occurrence of dot defects in images displayed ascaused by short-circuiting of the storage capacitor upper electrode iseffectively suppressed, the display quality is prevented fromdeteriorating, and a high manufacturing yield can be attained. The abovedisplay device is preferably a liquid crystal display device, amongothers.

The active matrix substrate of the invention has the constitutiondescribed above and each storage capacitor upper electrode comprisesthree or more divided electrodes in the region opposing the storagecapacitor wiring pattern or scanning signal line and, therefore, evenwhen the storage capacitor upper electrode is short-circuited with thestorage capacitor wiring pattern or scanning signal line due to aconductive foreign material or a pinhole in the insulating layer or withthe data signal line formed in the same step, it is possible toelectrically separate only the divided electrode containing the shortcircuit site to allow the remaining divided electrodes to functioneffectively and thereby maintain the function of the storage capacitorelement. Generally, both end portions of a storage capacitor upperelectrode are susceptible to short-circuiting because of there beingdisposed a data signal line, among others. Even when both dividedelectrodes at both ends are short-circuited, it is now possible to allowthe remaining divided electrode or electrodes to function effectivelyand thereby maintain the function of the storage capacitor element. Whensuch active matrix substrate is used as a pixel-electrode-disposedsubstrate in a display device such as a liquid crystal display device,the appearance of dot defects in images displayed as caused byshort-circuiting of the storage capacitor upper electrode can beeffectively suppressed, the display quality of the display device can beprevented from deteriorating, and the yield can be improved. Thus, theactive matrix substrate can be adequately used in a liquid crystalpanel, such as a large-size liquid crystal television, of which a highlevel of panel quality is required.

In the following, some typical examples are given and the presentinvention is described in further detail, referring to the drawings.These examples are, however, by no means limitative of the scope of theinvention.

EXAMPLE 1

In Example 1, referring to FIG. 1 and FIG. 2, a mode of practice usingthe Cs-on-Common system in which a storage capacitor (common) wiringpattern is formed as the storage capacitor lower electrode is described.

FIG. 1 is a schematic plan view illustrating the constitution of onepixel in an active matrix substrate in one mode of embodiment of theinvention, and FIG. 2 is a schematic sectional view showing a section ofthe active matrix substrate shown in FIG. 1 as cut along the line D-D′.

Referring to FIG. 1, in the active matrix substrate, a plurality ofpixel electrodes 21 is disposed to form a matrix. Around each of thesepixel electrodes 21, there are disposed, in a manner crossing with eachother, each scanning signal line 22 for scanning signal feeding, and adata signal line 23 for data signal feeding. At the crossing point ofthe scanning signal line 22 and data signal line 23, there is disposed aTFT 24 as a switching element to be connected to the pixel electrode 21.The scanning signal line 22 is connected to the gate electrode 32 ofthis TFT 24, and the TFT 24 is driven and controlled by a scanningsignal inputted into the gate electrode 32. The data signal line 23 isconnected to the source electrode 36 a of the TFT 24, and a data signalis inputted into the source electrode 36 a of the TFT 24. Further, tothe drain electrode 36 b, there are connected an interconnectionelectrode 25, one electrode of a storage capacitor element (storagecapacitor upper electrode) comprising three divided electrodes 25 a, 25b and 25 c via the interconnection electrode 25, and the pixel electrode21 via the interconnection electrode 25 and a contact hole 26 a. Astorage capacitor (common) wiring pattern 27 functions as the otherelectrode of the storage capacitor element (storage capacitor lowerelectrode).

Referring to FIG. 2, the gate electrode 32 connected to the scanningsignal line 22 is disposed on a transparent insulating substrate(insulating substrate) 31 made of glass, plastic or like material. Thescanning signal line 22 and gate electrode 32 are each formed of a layerof a metal such as titanium, chromium, aluminum or molybdenum or analloy thereof or a laminate thereof. A storage capacitor (common) wiringpattern 27 constituting the other electrode of the storage capacitorelement (storage capacitor lower electrode) is made of the same materialas the scanning signal line 22 and/or gate electrode 32. A gateinsulator 33 is formed on the scanning signal line 22, gate electrode 32and storage capacitor (common) wiring pattern 27 to cover these. Thegate insulator 33 is formed of an insulating layer, such as a siliconnitride or silicon oxide layer. Thereon is disposed a high-resistivitysemiconductor layer 34 made of amorphous silicon or polysilicon, forinstance, in a manner overlapping with the gate electrode 32. Furtherthereon is disposed a lower-resistivity semiconductor layer made of animpurity-doped n+ amorphous silicon to give the source electrode 36 aand drain electrode 36 b. The data signal line 23 is formed so as to beconnected to the source electrode 36 a. The interconnection electrode 25is disposed so as to be connected to the drain electrode 36 b, and theinterconnection electrode 25 is extended to constitute the storagecapacitor upper electrode, which serve as one electrode of the storagecapacitor element and comprise three divided electrodes 25 a, 25 b and25 c, and is connected to the pixel electrode 21 via the contact hole 26a. The data signal line 23, interconnection electrode 25, and thestorage capacitor upper electrode comprising three divided electrodes 25a, 25 b and 25 c are formed of the same material utilizing a layer of ametal such as titanium, chromium, aluminum or molybdenum or an alloythereof, or a laminate thereof. The pixel electrode 21 is formed of aconductive layer having transparency, such as an ITO, IZO, zinc oxide ortin oxide layer. The contact hole 26 a is formed so as to penetrate aninterlayer insulation layer 38 formed to cover the top surface each ofthe TFT 24, scanning signal line 22, data signal line 23 andinterconnection electrode 25. As the material of the interlayerinsulation layer 38, there may be mentioned, for example, acrylicresins, silicon nitride, and silicon oxide.

One electrode of the storage capacitor element (storage capacitor upperelectrode) is divided into three electrodes 25 a, 25 b and 25 c in theregion opposing the storage capacitor (common) wiring pattern 27, namelyin the region where the electrode overlaps with the storage capacitorwiring pattern 27 to form the storage capacitor element.

The interconnection electrode 25 is connected to the divided electrodes25 a, 25 b and 25 c, respectively so that, in case of short-circuitingof any of the divided electrodes 25 a, 25 b and 25 c, theshort-circuited divided electrode alone can be electrically separatedfrom the drain electrode 36 b of the TFT 24. When a short circuit isformed due to a residual layer 98, for instance, the interconnectionelectrode 25 is destructed for separation at the cleavage site K bymeans of a laser, for instance, whereby the short-circuited dividedelectrode can be readily separated from the drain electrode 36 b.

The contact hole 26 a is formed on the site other than the dividedelectrodes 25 a and 25 c, which are close to the data signal line 23,namely only on the divided electrode 25 b. The divided electrodes 25 aand 25 c are close to the data signal line 23 formed in the same stepand, therefore, are susceptible to short-circuiting with the data signalline 23 due to a residual layer 98 or the like as compared with thedivided electrode 25 b. Therefore, if contact holes are disposed on thedivided electrodes 25 a and 25 c and the divided electrodes 25 a or 25 cis short-circuited, not only the short-circuited divided electrodes 25 aor 25 c is to be separated from the drain electrode 36 b by destructionand separation at the cleavage site K on the interconnection electrode25 by means of a laser, for instance but also the pixel electrode 21 onthe contact hole located on the short-circuited divided electrodes 25 aor 25 c is destructed and separated. Thus, a step of separating thepixel electrode 21 from the short-circuited divided electrode 25 a or 25c becomes newly necessary. Therefore, the contact hole 26 a is disposedon the divided electrode 25 b, not on the divided electrodes 25 a or 25c susceptible to short-circuiting, to facilitate repairing in case ofshort-circuiting.

In cases where the reliability of contacting is doubtful due to suchproblems as difficulty in connecting a layer of ITO or the like to serveas the pixel electrode 21 in the contact hole 26 a with good coverageand a great difference in contact resistance between the metal layermade of aluminum, for instance, to serve as the storage capacitorelectrode and the layer of ITO, for instance, to serve as the pixelelectrode, the divided electrode(s) 25 a and/or 25 c may also beprovided with a contact hole.

The area of overlapping between the divided electrode 25 b, on which thecontact hole 26 a is disposed, and the storage capacitor (common) wiringpattern 27 is smaller than the areas of overlapping between the otherdivided electrodes 25 a and 25 c and the storage capacitor (common)wiring pattern 27. Such a structure makes it possible to reduce thepossibility of short-circuiting between the divided electrode 25 b andthe storage capacitor (common) wiring pattern 27 via the gate insulator33 due to the occurrence of a conductive foreign material or a pinhole99, since the area of overlapping between the divided electrode 25 b andthe storage capacitor (common) wiring pattern 27 is small as comparedwith the areas of overlapping between the other divided electrodes 25 aand 25 c, which are close to the data signal line 23, and the storagecapacitor (common) wiring pattern 27.

In the following, some examples of modification of Example 1 shown inFIG. 1 and FIG. 2 are further described.

In Example 1, the divided electrodes 25 a, 25 b and 25 c arequadrilateral in shape, as shown in FIG. 1. The shape is not limitedthereto but includes triangular, semicircular and trapezoidal shapes andothers. Thus, it is only necessary to dispose the storage capacitorupper electrodes on the gate insulator 33 in a manner overlapping withthe storage capacitor (common) wiring pattern 27 so that at least thedivided electrodes close to the data signal line 23 may be separatedfrom the other divided electrode or electrodes. The storage capacitorupper electrode shown in FIG. 1 consists of three divided electrodes 25a, 25 b and 25 c. The number of divisions (N) is not limited to 3 butmay be four or more, i.e. N≧3.

According to the above description, the storage capacitor (common)wiring pattern 27 is formed of the same material as the scanning signalline 22 and gate electrode 32. The material to be used is not limitedthereto. Thus, the storage capacitor (common) wiring pattern 27 may beformed using another material (e.g. an ITO or like transparentconductive material) before/after formation of the scanning signal line22 and/or gate electrode 32.

In Example 1, the interconnection electrode 25 is formed in the wiringpattern shown in FIG. 1. The wiring pattern is not limited thereto,however. Thus, it is only necessary that a part of the interconnectionelectrode 25 connected to the drain electrode 36 b be connected to thedivided electrodes 25 a, 25 b and 25 c, respectively so that, in case ofshort-circuiting of any of the divided electrodes 25 a, 25 b and 25 c,the short-circuited divided electrode alone can be electricallyseparated from the drain electrode 36 b of the TFT 24.

As for the insulating layer constituting the storage capacitor element,the gate insulator 33 alone is shown in FIG. 2 but this has nolimitative meaning. Thus, a further insulation layer other than the gateinsulating layer 33 may be formed on the storage capacitor (common)wiring pattern 27 before/after formation of the gate insulator 33.

EXAMPLE 2

In Example 2, referring to FIG. 3, a mode of practice using theCs-on-Gate system in which no storage capacitor (common) wiring patternis disposed but a neighboring scanning signal line is utilized as thestorage capacitor lower electrode is described.

FIG. 3 is a schematic plan view illustrating the constitution of onepixel in an active matrix substrate in a preferred mode of embodiment ofthe invention.

Referring to FIG. 3, in the active matrix substrate, a plurality ofpixel electrodes 21 is disposed to form a matrix. Around each of thesepixel electrodes, there are disposed, in a manner crossing with eachother, a scanning signal line 22 for scanning signal feeding, and a datasignal line 23 for data signal feeding. At the crossing point of thescanning signal line 22 and data signal line 23, there is disposed a TFT24 as a switching element to be connected to the pixel electrode 21. Thescanning signal line 22 is connected to the gate electrode of this TFT24, and the TFT 24 is driven and controlled by a scanning signalinputted into the gate electrode. The data signal line 23 is connectedto the source electrode of the TFT 24, and a data signal is inputtedinto the source electrode of the TFT 24. Further, to the drainelectrode, there are connected an interconnection electrode 25, oneelectrode of a storage capacitor element (storage capacitor upperelectrode) comprising four divided electrodes 25 d, 25 e, 25 f and 25 gvia the interconnection electrode 25, and the pixel electrode 21 via theinterconnection electrode 25 and contact holes 26 b and 26 c. Aneighboring scanning signal line 22′ is utilized as the other electrodeof the storage capacitor element (storage capacitor lower electrode).

One electrode of the storage capacitor element (storage capacitor upperelectrode) is divided into four divided electrodes 25 d, 25 e, 25 f and25 g in the region opposing the neighboring scanning signal line 22′,namely in the region overlapping with the pattern of the neighboringscanning signal line 22′ and forming the storage capacitor element.

The interconnection electrode 25 is connected to the divided electrodes25 d, 25 e, 25 f and 25 g, respectively so that, in case ofshort-circuiting of any of the divided electrodes 25 d, 25 e, 25 f and25 g, the short-circuited divided electrode alone can be electricallyseparated from the drain electrode of the TFT 24. When a short circuitis formed due to a residual layer, for instance, the interconnectionelectrode 25 is destructed for separation at the cleavage site K bymeans of a laser, for instance, whereby the short-circuited dividedelectrode can be readily separated from the drain electrode.

The contact holes 26 b and 26 c are formed on the sites other than thedivided electrodes 25 d and 25 g, which are close to the data signalline 23, namely only on the divided electrodes 25 e and 25 f.

The divided electrodes 25 d and 25 g are close to the data signal line23 formed in the same step and, therefore, are susceptible toshort-circuiting with the data signal line 23 due to a residual layer,any conductive foreign material or the like as compared with the dividedelectrodes 25 e and 25 f. Therefore, if contact holes are disposed onthe divided electrodes 25 d and 25 g and the divided electrode 25 d or25 g is short-circuited, not only the short-circuited divided electrode25 d or 25 g is to be separated from the drain electrode of the TFT 24by destruction and separation at the cleavage site K on theinterconnection electrode 25 by a laser, for instance but also thecontact hole located on the short-circuited divided electrode 25 d or 25g is destructed and separated. Thus, a step of separating that dividedelectrode also from the pixel electrode 21 becomes newly necessary.Therefore, the contact holes 26 b and 26 c are disposed on the dividedelectrodes 25 e and 25 f, not on the divided electrodes 25 d or 25 gsusceptible to short-circuiting, to facilitate repairing in case ofshort-circuiting.

In cases where the reliability of contacting is doubtful due to suchproblems as difficulty in forming a layer of ITO or the like to serve asthe pixel electrode 21 in the contact holes 26 b and 26 c with goodcoverage and a great difference in contact resistance between the metallayer made of aluminum, for instance, to serve as the storage capacitorupper electrode and the layer of ITO, for instance, to serve as thepixel electrode, the divided electrode(s) 25 d and/or 25 g may also beprovided with a contact hole.

The areas of overlapping between the divided electrodes 25 e and 25 f,on which the contact holes 26 b and 26 c are disposed, and theneighboring scanning signal line 22′ are smaller than the areas ofoverlapping between the other divided electrodes 25 d and 25 g and theneighboring scanning signal line 22′. Such a structure makes it possibleto reduce the possibility of short-circuiting between the dividedelectrodes 25 e and 25 f and the neighboring scanning signal line 22′via an insulating layer constituting the storage capacitor element dueto the occurrence of a conductive foreign material or a pinhole, sincethe areas of overlapping between the divided electrodes 25 e and 25 fand the neighboring scanning signal line 22′ are small as compared withthe areas of overlapping between the other divided electrodes 25 d and25 g and the neighboring scanning signal line 22′.

In the following, some examples of modification of Example 2 shown inFIG. 3 are further described.

In Example 2, the divided electrodes 25 d, 25 e, 25 f and 25 g arequadrilateral in shape, as shown in FIG. 3. The shape is not limitedthereto but includes triangular, semicircular and trapezoidal shapes andothers. Thus, it is only necessary to dispose the storage capacitorupper electrodes on the insulating layer of the storage capacitorelement in a manner overlapping with the pattern of the neighboringscanning signal line 22′ so that at least the divided electrodes closeto the data signal line 23 may be separated from the other dividedelectrode or electrodes. The storage capacitor upper electrode shown inFIG. 3 consists of four divided electrodes 25 d, 25 e, 25 f and 25 g.The number of divisions (N) is not limited to 4 but the necessarycondition is that N≧3.

In Example 2, the interconnection electrode 25 is formed in the wiringpattern shown in FIG. 3. The wiring pattern is not limited thereto,however. Thus, it is only necessary that a part of the interconnectionelectrode 25 connected to the drain electrode be connected to thedivided electrodes 25 d, 25 e, 25 f and 25 g, respectively so that, incase of short-circuiting of any of the divided electrodes 25 d, 25 e, 25f and 25 g, the short-circuited divided electrode alone can beelectrically separated from the drain electrode of the TFT 24.

EXAMPLE 3

In Example 3, referring to FIG. 6, a mode of practice using theCs-on-Common system in which a drain electrode is connected to a storagecapacitor upper electrode via an interconnection wiring pattern isdescribed.

FIG. 6 is a schematic plan view illustrating the constitution of onepixel on an active matrix substrate in a preferred mode of embodiment ofthe invention.

Referring to FIG. 6, in the active matrix substrate, a plurality ofpixel electrodes 21 is disposed to form a matrix. Around each of thesepixel electrodes 21, there are disposed, in a manner crossing with eachother, a scanning signal line 22 for scanning signal feeding, and a datasignal line 23 for data signal feeding. At the crossing point of thescanning signal line 22 and data signal line 23, there is disposed a TFT24 as a switching element to be connected to the pixel electrode 21. Thescanning signal line 22 is connected to the gate electrode of this TFT24, and the TFT 24 is driven and controlled by a scanning signalinputted into the gate electrode. The data signal line 23 is connectedto the source electrode of the TFT 24, and a data signal is inputtedinto the source electrode of the TFT 24. Further, to the drainelectrode, there are connected an interconnection electrode 25, oneelectrode of a storage capacitor element (storage capacitor upperelectrode) 25 b via the interconnection electrode 25, and the pixelelectrode 21 via the interconnection electrode 25 and a contact hole 26b.

One electrode of the storage capacitor element (storage capacitor upperelectrode) is divided into three divided electrodes 25 a, 25 b and 25 cin the region opposing a storage capacitor wiring pattern 27, namely inthe region of overlapping of the electrode with the storage capacitorwiring pattern 27 to form the storage capacitor element. Thisconstitution makes it possible, in case of short-circuiting of at leastone of the divided electrodes 25 a and 25 c at both ends, which areclose to the data signal line, to separate the short-circuited dividedelectrode 25 a and/or 25 c from the pixel electrode 21 by means of alaser or the like (namely eliminate the pixel electrode on and aroundthe contact hole 26 a and/or 26 c) to thereby allow the remainingdivided electrode(s) to function effectively and thus maintain thefunction of the storage capacitor element.

The interconnection electrode 25 is connected only to the middle dividedelectrode 25 b, which does not neighbor the data signal line 23, amongthe three divided electrodes 25 a, 25 b and 25 c. The divided electrodes25 a and 25 c neighboring the data signal line 23 are connected to thepixel electrode 21 via the contact holes 26 a and 26 c, respectively,and further connected to the drain electrode of the thin film transistor24 via the pixel electrode 21. The divided electrodes 25 a, 25 b and 25c, together with the storage capacitor wiring pattern 27, constitute thestorage capacitor element.

In this example, the interconnection electrode 25 is not connected toall the divided electrodes 25 a, 25 b and 25 c but only to one dividedelectrode 25 b, and the number of lines and routes of theinterconnection electrode 25 can thereby be reduced. Therefore, the areaof the interconnection electrode 25, which becomes a light-shieldingarea, can be reduced and, thus, the aperture ratio can be prevented fromlowering. When the divided electrodes 25 a and 25 c are connected onlyto the pixel electrode 21 via the contact holes 26 a and 26 c but arenot connected to the interconnection electrode 25, as in this example,it is not necessary, in case of short-circuiting of the dividedelectrodes 25 a or/and 25 c with the data signal line 23 orinterlayer-short-circuiting thereof with the storage capacitor wiringpattern 27, to electrically separate the interconnection electrode 25from the divided electrodes 25 a or/and 25 c on the occasion ofrepairing, hence the addition of a new step can be avoided.

In the following, some examples of modification of Example 3 are furtherdescribed.

In this example, the interconnection electrode 25 is connected to themiddle divided electrode 25 b among the three divided electrodes 25 a,25 b and 25 c. This has no limitative meaning, however. Thus, whencontact holes 26 a, 26 b and 26 c are disposed on the respective dividedelectrodes 25 a, 25 b and 25 c and the all divided electrodes 25 a, 25 band 25 c are connected to the pixel electrode 21 via the contact holes26 a, 26 b and 26 c and the interconnection electrode 25 is connected toat least one of the divided electrodes 25 a, 25 b and 25 c, all thedivided electrodes 25 a, 25 b and 25 c can be connected to the drainelectrode of the thin film transistor 24.

In this example, too, the shape of the divided electrodes 25 a, 25 b and25 c, the number of divided electrodes, and the pattern of theinterconnection electrode 25 are not particularly restricted to thosedescribed, like in Example 1.

EXAMPLE 4

In Example 4, referring to FIG. 7, a mode of practice using theCs-on-Common system in which a drain electrode is connected to a pixelelectrode directly via a contact hole without passing through anyinterconnection electrode.

FIG. 7 is a schematic plan view illustrating the constitution of onepixel in an active matrix substrate in a preferred mode of embodiment ofthe invention.

Referring to FIG. 7, in the active matrix substrate, a plurality ofpixel electrodes 21 is disposed to form a matrix. Around each of thesepixel electrodes 21, there are disposed, in a manner crossing with eachother, a scanning signal line 22 for scanning signal feeding, and a datasignal line 23 for data signal feeding. At the crossing point of thescanning signal line 22 and data signal line 23, there is disposed a TFT24 as a switching element to be connected to the pixel electrode 21. Thescanning signal line 22 is connected to the gate electrode of this TFT24, and the TFT 24 is driven and controlled by a scanning signalinputted into the gate electrode. The data signal line 23 is connectedto the source electrode of the TFT 24, and a data signal is inputtedinto the source electrode of the TFT 24. Further, to the drainelectrode, there is connected the pixel electrode 21 via a contact hole28. One electrode of a storage capacitor element (storage capacitorupper electrode) comprising divided electrodes 25 a, 25 b and 25 c isconnected to the pixel electrode 21 via contact holes 26 a, 26 b and 26c, and constitutes, together with a storage capacitor wiring pattern 27,the storage capacitor element. Thus, there is no interconnectionelectrode disposed, and the drain electrode of the TFT 24 is connectedto the storage capacitor upper electrode comprising divided electrodes25 a, 25 b and 25 c via the contact holes 26 a, 26 b and 26 c formed onthe respective divided electrodes 25 a, 25 b and 25 c, the pixelelectrode 21 and the contact hole 28.

One electrode of the storage capacitor element (storage capacitor upperelectrode) is divided into three divided electrodes 25 a, 25 b and 25 cin the region opposing a storage capacitor wiring pattern 27, namely inthe region of overlapping of the electrode with the storage capacitorwiring pattern 27 to form the storage capacitor element. Thisconstitution makes it possible, even in case of short-circuiting of oneor two of the divided electrodes, to separate the short-circuiteddivided electrode(s) from the pixel electrode 21 by means of a laser,for instance, to thereby allow the remaining divided electrode(s) tofunction effectively and thus maintain the function of the storagecapacitor element. Further, this constitution in which nointerconnection electrode is present makes it possible to prevent theaperture ratio from decreasing due to the occurrence of aninterconnection electrode as compared with the constitution in which thedrain electrode and storage capacitor wiring pattern are connected toeach other via an interconnection electrode.

In this example, too, the shapes of the divided electrodes 25 a, 25 band 25 c, or the number of divided electrodes is not particularlyrestricted, like in Example 1.

1. An active matrix substrate, comprising: a thin film transistor, ascanning signal line, and a data signal line disposed on the substrate,a gate electrode of the transistor being connected to the scanningsignal line, a source electrode thereof being connected to the datasignal line, and a drain electrode thereof being connected to a pixelelectrode; and an upper electrode disposed so as to oppose a storagecapacitor wiring pattern at least via an insulating layer, wherein,within a pixel region, the upper electrode includes three dividedelectrodes in a region opposing the storage capacitor wiring pattern,and a central divided electrode of the three divided electrodes has thesmallest area.
 2. The active matrix substrate according to claim 1,wherein each of the divided electrodes is connected to the pixelelectrode via a contact hole, and the contact hole is in a regionopposing the storage capacitor wiring pattern.
 3. An active matrixsubstrate, comprising: a thin film transistor, a scanning signal line,and a data signal line disposed on the substrate, a gate electrode ofthe transistor being connected to the scanning signal line, a sourceelectrode thereof being connected to the data signal line, and a drainelectrode thereof being connected to a pixel electrode; and an upperelectrode disposed so as to oppose a storage capacitor wiring pattern atleast via an insulating layer, wherein, within a pixel region, the upperelectrode includes three divided electrodes in a region opposing thestorage capacitor wiring pattern and at least two of the three dividedelectrodes having different shapes, and a central divided electrode ofthe three divided electrodes has the smallest area.
 4. The active matrixsubstrate according to claim 3, wherein each of the divided electrodesis connected to the pixel electrode via a contact hole, and the contacthole is in a region opposing the storage capacitor wiring pattern.
 5. Anactive matrix substrate, comprising: a thin film transistor, a scanningsignal line, and a data signal line disposed on the substrate, a gateelectrode of the transistor being connected to the scanning signal line,a source electrode thereof being connected to the data signal line, anda drain electrode thereof being connected to an interconnectionelectrode; and an upper electrode disposed so as to oppose a storagecapacitor wiring pattern at least via an insulating layer and connectedto the interconnection electrode and a pixel electrode, wherein theupper electrode comprises three divided electrodes in a region opposingthe storage capacitor wiring pattern, and wherein the interconnectionelectrode is connected only to a central divided electrode of the threedivided electrodes.